mansion in the mist glitch

so i ran the mansion in the mist and the boss will not activate, i ran it once and everything went well on the second run after using vision of paradise precursor tablet so you have all the info the boss would not start when entering the arena i then cleared the whole map on all monsters and then went back in still nothing so I'm moving on just wanted to let some one know this happened so it can be fixed.

Can confirm some times I couldn't find that door to the boss area even after clearing. It seems to be random.

mansion in the mist the boss will not activate a again whole map cleared boss fight wont start this is very frustrating. lost both runs this time as i used a tablet that allows you to run twice and it glitch on the first run.

also the stairs to return downstairs are gone

Happened to me. I got the boss fight to start after going to the vaal ruins via the portal and then return back to the map.